This invention relates to a diaphragm filtration system which comprises a plurality of parallel-arranged pipes having terminal enlargements; a plurality of return bends, each interconnecting adjoining ends of two adjacent pipes. In each pipe, there is disposed a diaphragm (arranged substantially coaxially with the pipe) which is supported by sleeves arranged at the pipe ends and which either engages directly face-to-face the inner wall of the associated pipe or is separated therefrom by a support layer which may be fixedly attached to the diaphragm. Adjoining two pipes are secured, at their terminal enlargement, to a base plate of the associated return bend; in the zone of connection between pipe and base plate, there is provided, either in the thickened pipe end or in the base plate, a recess for receiving a sealing element.
A diaphragm filtration system of the above-outlined structure is disclosed in U.S. patent application Ser. No. 703,846 (Grabow et al), filed July 9, 1976. According to the disclosure in that application, the diaphragms are of hose-like structure, that is, the cross section of the diaphragm is an annulus of integral (continuous) area. Similarly structured, known diaphragm filtration systems have since exclusively been equipped with hose diaphragms although the difficulties and disadvantages involved in their use have been well known.
It is thus a disadvantage of hose-shaped diaphragms that their manufacture with small diametrical tolerances has encountered technical difficulties and has generated high manufacturing costs. Further, the pipes of the diaphragm filtration system have, regarding their inner diameter, and the support layers have, regarding their thicknesses, tolerances of such a range that the hose diaphragms which are arranged in the pipes or, as the case may be, on the support layers, are often damaged by fold formation or excessive expansion. Further, because of the expensive manufacture, diaphragm hoses are available only in limited predetermined diameters and, consequently, the design engineer is compelled to adapt the structural data of the diaphragm filtration system to the given diameter of the hose diaphragm. In this manner, many, technically advantageous solutions had to remain unexploited. Also, the different hose diaphragm types can be shipped and stored only in expensive water containers.